3/4/2019 Feedback Loops
Name:
Feedback Loops: Insulin and Glucagon
The control of blood sugar (glucose) by insulin is a good example of a negative feedback mechanism. When blood sugar rises, receptors in the
body sense a change. In turn, the control center (pancreas) secretes insulin into the blood effectively lowering blood sugar levels. Once blood
sugar levels reach homeostasis, the pancreas stops releasing insulin. Examine the graphic below to understand how this feedback loop works.
Body cells take up glucose.
Insulin
PANCREAS
Beta cells in pancreas Liver takes up
release insulin into the blood, glucose and
stores it as LIVER
glycogen.
STIMULUS: blood
glucose level rises.
Homeostasis Blood glucose
level declines.
(glucose levels 90mg/100mL)
2 Set Point
STIMULUS: blood
glucose level falls.
Blood glucose
level rises.
Liver breaks
Alpha cells in pancreas
down glycogen
release glucagon.
and releases
PANCREA glucose
LIVER
Glucagon biologycorner.com
1. The image shows Wvo different types of stimuli (1 and 2), but doesn't explain what the stimuli is that causes
blood sugar to raise or lower. Based on clues in the graphic, what are the two stimuli?
Eating food makes blood sugar rise and Being hungry
makes blood sugar drop
2. What happens when your blood sugar rises?
The pancreas releases insulin
3. What is the effect of glucagon? What cells release glucagon?
Glucagon causes the liver to break down glycogen to release glucose
alpha cells
4. What is the effect of insulin? What cells release insulin?
insulin causes cells to take up the sugar
beta cells
5. What is the normal level of glucose in the blood? Why is this called a "set point."
90mg/100mL
the pancreas will release insulin in response to sugar in the blood
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3/4/2019 Feedback Loops
6. What would you expect to happen if your blood sugar was 120 mg / 100 mL ? Be specific.
Insulin will be secreted by the pancreas
7. A person with diabetes cannot regulate their blood sugar, mainly because the pancreas does not release enough insulin. To treat the
disease, a person must monitor their blood sugar, if their blood sugar is high, they must take an injection of insulin. How do you think they would
need to treat low blood sugar?
if they have low blood sugar, they will need to consume foods that are high in sugar
8. In a single sentence, explain the relationship between the pancreas and homeostasis.
pancreas maintains homeostasis by regulating the level of sugar
9. Where does the glucose that is released into the blood ultimately end up (2 places)?
body cells
liver
10. Explain how the thermostat in your house uses a negative feedback system to maintain your home's temperature.
As the temperature in the house drops, the thermostat will detect this change and send a signal to the furnace to heat
up the house
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